Wrap OpenCV Mat as numpyarray hangs ?

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Hi, I am using opencv v3.4.2 with QT Creator IDE in C++.

I am trying to wrap an OpenCV matrix (Mat) as a numpyarray (PyObject *) so that I can pass it to a python script for processing. I am using the built-in wrapper functions from here: opencv/cv2.cpp. In particular this function:

PyObject* pyopencv_from(const Mat& m)
{
    if( !m.data )
        Py_RETURN_NONE;
    Mat temp, *p = (Mat*)&m;
    if(!p->u || p->allocator != &g_numpyAllocator)
    {
        temp.allocator = &g_numpyAllocator;
        ERRWRAP2(m.copyTo(temp));
        p = &temp;
    }
    PyObject* o = (PyObject*)p->u->userdata;
    Py_INCREF(o);
    return o;
}

So I have something like this:

Mat frame;
/*frame is populated*/
PyObject* pMat = opencv_from(frame);

The code compiles fine but when I call the function it hangs on m.copyTo(temp).

Does anyone have any advice on why this is not working ? Thanks.